This invention relates to an improved swivel seat pedestal for use on moveable apparatus. More particularly, this invention relates to a swivel seat pedestal safely usable on industrial and commercial machinery of the type on which an operator's seat is subjected to severe vibrations during use of the machinery.
On industrial machinery, the operator's seat is often subject to a variety of forces, including severe vibration, vertical and lateral jarring, and torsional loads from the operator's constantly shifting weight. These forces sometimes cause significant stress on the support structure for the seat.
For fixed, non-rotatable seats, this vibration is not difficult to safely accommodate. The seat can easily be rigidly and safely secured to the support structure in many well known ways. Similarly, a seat belt, if required, can easily be rigidly and safely secured to either the non-rotatable seat or directly to the support structure.
Frequently, however, the operator's seat should be rotatable so the operator can rotate the seat to accomplish different tasks on the machinery. This necessarily complicates the design of the seat if the seat, while rotatable, is to remain capable of withstanding severe vibration, shock, and torsion.
One popular prior art swivel seat for industrial machinery has a swivel plate mounted on a pivot bolt secured to a supporting, rigid base plate. Polyethylene sheet is sandwiched between the plates to reduce friction.
Although this swivel seat is economical and easy to manufacture, it depends entirely on the pivot bolt to provide lateral stability to the seat. Thus, the single pivot bolt must accommodate and transfer to the support structure all the lateral vibration and shock loads placed on the seat as well as bending loads on the bolt caused by the constantly shifting weight of the operator on the seat or against the seat belt, if secured to the swivel plate.
Another type of prior art seat uses both a central pivot bolt and a bearing and race mechanism to support a swivel plate on a base plate. Although the pivot bolt and bearing and race system provides both rotatability and greater lateral and torsional stability to the seat, it is also relatively expensive to manufacture and difficult to assemble.
Other bearing and race supported seats are shown in U.S. Pat. Nos. 1,711,268, 1,735,320, and 3,570,800. For example, U.S. Pat. No. 1,711,268, to Kilburn, shows a rotatable seat for use on a railcar. This seat provides lateral and torsional stability by (i) a bearing and race support structure, (ii) a center pin, (iii) two interengaging flanges, one secured to the swivel plate and the other to the base plate, and (iv) arm rest supports secured to a wall of the railcar.
The result is that these seats in the prior art have been either (a) relatively inexpensive and easy to manufacture, but dependent on a single pivot pin to provide lateral stability, or else (b) more complicated, expensive, and difficult to assemble.
It is therefore an object of the present invention to provide a swivel seat pedestal that is relatively inexpensive and easy to manufacture than the seats in the prior art. Another object is to provide a swivel seat pedestal that is not solely dependent on a single pivot bolt to provide lateral stability to the seat under severe conditions. Yet another object is to simultaneously provide such a seat with greater torsional stability than that provided by seats with the single pivot bolt for lateral stability.
A further object of this invention is to provide a swivel seat pedestal that is less complicated than the pedestals of the prior art and is, preferrably, without a bearing or race mechanism. An additional object is to provide a swivel seat pedestal that can safely accommodate a seat belt secured to the rotatable seat rather than the support apparatus.
There are other objects and advantages of the present invention. They will become apparent as the specification proceeds.